1. Field of the Invention
The present invention is related to a method of making low profile fine wire interconnections with an automatic wire bonder. More particularly, the present method is preferably employed to make wire interconnections between a pad on a semiconductor device and a lead frame finger of a Thin Small Outline Package (TSOP). Such packages provide only a small separation between the top of the semiconductor die and the top of the package, thus requiring that the fine wire maintain a minimum clearance between the top of the package and the semiconductor die.
2. Description of the Prior Art
Automatic wire bonders for making fine wire interconnections have been commercially available for about two decades. Until recently there were device applications which required extremely thin packages such as Smart Cards, which comprise a small microprocessor or active logic and may comprise some memory which could not be ball wire bonded. Such devices could only be bonded using Tape Automatic Bonding (TAB) or flip-chip bonding techniques or equivalents thereof.
Our U.S. Pat. No. 5,111,989 teaches a method of making low profile fine wire interconnections which may be used with automatic wire bonders to bond such thin package devices. The method taught in this patent is an acceptable solution to bonding low profile devices where the pads on the die are all located at the outer perimeter, thus do not involve die clearance problems. However, when the die or chip has lead out pads that are either internal to the die area or set back from the edge of the die an excessive amount or the die pad bonding point and/or the lead out bonding points require long wire excursions over the die, the fine wire interconnection loop shape causes height interference or probable interference at the edge of the die. If the loop height is increased or looped excessively to clear the die surface and/or the die edge, then the maximum height above the die becomes excessive for the aforementioned TSOP packages.
Accordingly, it would be desirable to provide a method of directing an automatic wire bonder to create a low profile fine wire interconnection with a constant clearance link above a semiconductor die before descending to the second bonding point on the lead frame.